The present invention relates to an image processing system and method for detecting a specific pattern from the image data, which is read out every pixel from an original document image by an image input device, or the image data received from communication means, and an image forming apparatus.
Recently, an illegal copying preventing system is proposed and applied to image forming apparatuses, such as full-color copying machines. In the system, specific patterns, e.g., two-dimensional codes, are buried in books, important documents, securities or the like. The system recognizes this pattern to prevent the illegal copying of those books or the like, or the illegal use of them.
Generally, the copying machine reads image information on an original document located at a given position, and copies it at the size of the original or at a magnification level set by the user. Accordingly, the unit for recognizing the specific pattern in the copying machine can easily recognize whether or not input image data has been magnified, and when it is magnified, recognize a magnification level at which the input image data has been increased in size, and hence it can carry out a discriminating process on the basis of the magnification information.
A printer, unlike the copying machine, is connected to an external machine, e.g., a personal computer (abbreviated simply as a PC), and receives image data to be output from the external machine. Let us consider a case where an original document containing a specific pattern buried therein in advance is read by an image reader, such as a scanner, the image data read out is loaded into the memory of the PC, the image data is magnified by several %, and the resultant data is sent to the printer. In this case, a magnification of the image data is unknown to the pattern recognizing unit in the printer. Therefore, the pattern recognizing unit will mistakenly judge that the specific pattern in the magnified image data is different in size from the specific pattern to be detected, and will fail to recognize the specific pattern of the magnified image data as the specific pattern to be detected.
To prevent such a pattern recognition failure in advance, there are known magnification-estimating techniques, which are employed for an image recognition device for recognizing the specific pattern (the Unexamined Japanese Patent Application Publication No. Hei 9-81729 and the Unexamined Japanese Patent Application Publication No. Hei 10-126614). The technique disclosed in the publication of the Unexamined Japanese Patent Application Publication No. Hei 9-81729 uses a plurality of matching reference images, such as an image having an average or typical characteristic of a specific pattern to be recognized, an image having a maximum characteristic, and an image having a minimum characteristic. The technique carries out a process of matching of an object image to be matched against the reference images to obtain a position where a peak degree of matching and degrees of matching of the object image. The technique carries out an interpolation process using the results of the matching process to produce a magnification of the object image.
The technique of the publication of the Unexamined Japanese Patent Application Publication No. Hei 10-126614 first detects a given mark contained in input image data, and then estimates a magnification given to the input image data on the basis of the size of the mark. The technique carries out a process of normalizing the input image on the basis of the estimated magnification, and compares the result of the normalization with reference data to discriminate whether or not an object image is contained in the input image.
The technique of the publication of the Unexamined Japanese Patent Application Publication No. Hei 9-81729 cannot handle the object images of patterns other than a circular pattern, however. There are cases that a pattern of the object image is not circular, that the object image is circular in pattern but the area within the circular contour contains complex patterns, and that an image intentionally rotated is input. To cope with such, a matching process is needed for the rotated image. To realize the matching process for the rotated image by a hardware technique, a circuit for executing the matching process will be large in circuit scale. To realize the matching process for the rotated image by a software technique, a fairly large amount of calculations will be required.
In the technique of the publication of the Unexamined Japanese Patent Application Publication No. Hei 10-126614, as described above, complicated steps are required for the process to judge whether or not an object image is contained in the object image. Accordingly, the technique needs a complex process.
Further, to judge whether or not an object image is present in the input image, the input image or the image internally processed is temporarily stored in a memory. To this end, a large memory will be used indispensably.